Circular knitting machines have traditionally used a tool having a stem (needle shank) whose lower surface touches the bottom of a thin groove into which the tool is inserted or whose upper face is at approximately the same height as the upper end face of the thin groove into which the tool is inserted.
When a circular knitting machine using such tool is operated continuously at high speed, the tool and the side faces of the thin groove come into contact with each other, generating frictional heat. To explain this point in detail, we will take a latch needle as an example of the tool used in a circular knitting machine. As shown in FIG. 2, a latch needle 10 is inserted into a thin groove 19 of the cylinder of the circular knitting machine. It rotates at high speed while sliding up and down. As the cylinder rotates, the latch needle 10 tends to tilt in the direction opposite to the rotating direction because of the inertia of movement. At this time, as indicated by an oval A in FIG. 2(b), the latch needle 10 and the thin groove 19 come into contact with each other at the upper end 21, and as indicated by an oval B in FIG. 2(b) and FIG. 2(c), the latch needle 10 and the thin groove 19 come into contact with each other at the lower end 20 of the thin groove, generating frictional heat. This significantly raises the temperature of the circular knitting machine, leading to thermal expansion of the circular knitting machine. This causes the following problems.
(1) The circular knitting machine can seize up if the gears of the gearing that drives the circular knitting machine are assembled with no play between each gear.
(2) The yarn-feeding tension of the knitting yarn supplied to the circular knitting machine can vary, resulting in different loop shapes of the knit fabric between immediately after the machine has started and after the machine has run for a long time.
(3) In a super large circular knitting machine such as those having a diameter of 60 inches, the diameter of the cylinder increases because of the heat expansion, narrowing the gap between the cylinder and the cam holder. This necessitates the gap between the cylinder and the cam holder to be designed with an extra margin.
FIG. 2 used in the above explanation is a cross section diagram illustrating a latch needle of the present invention. With respect to the cross section of the butt, the present invention has the same defect as prior art.
In order to solve this problem, a knitting needle for a knitting machine, disclosed in Patent Document 1 listed below, has an elongate groove extending longitudinally along at least one of the broad sides of a needle shank, thereby reducing the area that comes in contact with the side faces of the needle groove.
A knitting needle for a knitting machine, disclosed in Patent Document 2 listed below, has a concavity on at least one of the broad sides of the needle stem, thereby reducing the area that comes in contact with the side faces of the needle groove.
A knitting needle for a knitting machine, disclosed in Patent Document 3 listed below, also has a concavity on at least one of the broad sides of the needle stem, thereby reducing the area that comes in contact with the side faces of the needle groove.
A knitting needle for a knitting machine, disclosed in Patent Document 4 listed below, has a cutout on the side of the needle stem, thereby giving it a shape that meanders along its thickness.
A knitting needle for a knitting machine, disclosed in Patent Document 5 listed below, has a shock-absorbing tool made of a curved spring at the position adjacent to the butt.
A knitting needle for a knitting machine, disclosed in Patent Document 6 listed below, has a concave groove for engaging a stitch-supply-side raising cam on the stem.
Patent Document 1: U.S. Pat. No. 4,625,527
Patent Document 2: U.S. Pat. No. 6,122,938
Patent Document 3: JP-B-3231648
Patent Document 4: JP-U-60-127387
Patent Document 5: U.S. Pat. No. 5,154,069
Patent Document 6: JP-A-59-1750